PSNR bsed comparisson of images

Sir, I have 4 images A,B,C,D and I have to compare image A using psnr, with respect to A,B,C and D. please suggest the code

Answer 1

[Image Analyst]

There is a function psnr() in the Image Processing Toolbox. If you don't have that, you can do it manually yourself. See my attached program.

[Mangesh]

Sir, I have the psnr.m, but how to use this psnr value in else if condition to compare images, please guide

[Image Analyst]

Why would there be an if/else block??? What would you be testing/checking/comparing in the if statement? Anyway I'm sure (or at least I'd like to think) that you know how to use an if/else statement

if someExpression
  % Do something such as call psnr
elseif someOtherExpression
  % Do something else
else
  % When all else fails, do this
end

[Mangesh]

Sir I have four images with same color but different contrast,with respective psnr values. Now I have to compare A with rest of the three that in how much percent it matches with rest of three.......please help